This application claims priority to Japanese patent application serial numbers 2001-57158 and 2001-238392, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a blade clamping devices that can be utilized, e.g., with jigsaws and other reciprocating tools.
2. Description of the Related Art
A known blade clamping device for a jigsaw is taught in U.S. Pat. No. 5,306,025. This blade clamping device affixes a saw blade to a reciprocating drive shaft or plunger. The blade clamping device includes a centering sleeve that extends from the drive shaft and the centering sleeve includes an external threaded section. A clamping sleeve is rotatably mounted on the external threaded section of the centering sleeve. By rotating the clamping sleeve about the longitudinal axis of the drive shaft and the centering sleeve, the blade clamping device can be moved from a blade locking position (blade clamping position) to a blade replacement position. In the blade replacement position, the saw blade can be removed from the blade clamping device and a new saw blade can be inserted into the blade clamping device. The blade clamping device is then locked in the blade locking position by rotating the clamping sleeve back to the blade locking position. A torsion spring normally biases the clamping sleeve towards the blade locking position.
A connecting bush (collar) is rotatably mounted around the clamping sleeve. The connecting bush includes a gripping member (tab) that extends through an aperture defined in the jigsaw housing. The connecting bush is operably coupled to the clamping sleeve, such that rotating or pivoting the gripping member with respect to the jigsaw housing will cause the clamping sleeve to rotate. However, during a sawing operation, the connecting bush does not contact the clamping sleeve. Therefore, the blade clamping device can freely reciprocate together with the drive shaft without interference from the connecting bush. Further, the gripping member allows the operator to rotate or pivot the clamping sleeve to the blade replacement position without directly touching the clamping sleeve.
However, the clamping sleeve of U.S. Pat. No. 5,306,025 can rotate past the blade replacement position (i.e., the rotational range of the clamping sleeve is not restricted). Therefore, in order to remove the saw blade from the blade clamping device, the clamping sleeve must be accurately and precisely rotated to the blade replacement position, so that the saw blade receiving slots within the blade clamping device will properly align. If the clamping sleeve is not accurately and precisely positioned in the blade replacement position, the saw blade can not be easily removed from the blade clamping device, because the blade slots are not aligned, and thus, a saw blade can not be inserted into or removed from the blade clamping device.
In order to accurately define the blade replacement position, the aperture in the jigsaw housing is designed so that the gripping member of the connecting bush abuts an edge of the aperture when the clamping device reaches the blade replacement position. Thus, the aperture of the jigsaw housing is designed to limit the pivotal range of the clamping sleeve, so that the clamping sleeve will stop at the blade replacement position.
Consequently, the relative positional relationships of the clamping sleeve, the connection bush, the gripping member and the jigsaw housing aperture are critical for accurately determining the blade replacement position. If all of these structures are not accurately manufactured and/or accurately positioned during assembly, it may be difficult or impossible to accurately position the blade clamping device in the blade replacement position. Therefore, this known design suffers a significant drawback in being difficult to accurately and reliably design and manufacture.
It is, accordingly, one object of the present teachings to teach blade clamps or blade clamping devices that facilitate accurate and reliable positioning of the blade replacement position using relatively simple structures. Such blade clamps may be advantageously utilized with blades having positioning projections (or dogs) extending from respective sides of the blade, although the present teachings are not limited to such blades.
Thus, in one embodiment of the present teachings, jigsaws are taught as representative examples of reciprocating power tools that are particularly suited for the present blade clamps. Naturally, the present teachings are not limited to jigsaws and the present blade clamps can be advantageously utilized in a variety of applications and with a variety of tools.
Generally speaking, jigsaws may include a housing, a reciprocating drive shaft driven by a motor, a blade clamp and a saw blade. The drive shaft is also known in the art as a plunger or a spindle and such terms are interchangeable. In one embodiment of the present teachings, the blade clamp may include a tab that can be manually rotated or pivoted by the operator of the jigsaw. Further, the blade clamp may preferably include a stopper that accurately stops the blade clamp in the blade replacement position. Therefore, it is not necessary to utilize an aperture in the jigsaw housing as a means for accurately stopping the blade clamp in the blade replacement position. Instead, the stopper is preferably disposed internally within the blade clamp and thus, can more reliably and accurately position the blade clamp in the blade replacement position than known blade clamps. Consequently, the blade replacement position is not determined by the relative positional relationships of the tab or gripper member and the aperture of the power tool housing, thereby enabling the construction of more reliable blade clamping devices.
Optionally, the jigsaw may include an electric motor that serves as a drive source for the drive shaft. Further, a transmission optionally may be included to convert rotational movement of the drive source into substantially linear reciprocating movement of the drive shaft. A variety of drives sources and transmissions may be utilized with the present teachings and the present blade clamps are not limited to any particular drive source and/or transmission.
The present blade clamps may be affixed to a distal end of the drive shaft. Further, the present blade clamps may generally include a rod, a pushpin, and a rotatable sleeve. Further, a pivotable or rotatable collar may be disposed around the rotatable sleeve and preferably may be pivotally coupled to the housing. The collar may selectively engage the rotatable sleeve so as to rotate the blade clamp to the blade replacement position. The collar may preferably include a tab or other gripping member that permits the operator to manually manipulate the collar in order to rotate or pivot to the collar, and thereby pivot or rotate the blade clamp to the blade replacement position.
In one embodiment of the present teachings, the rod may be affixed to a lower or distal end of the drive shaft. A blade receiving portion (recess) may be defined within the rod. A base end of the blade may be inserted into the blade receiving portion so that the longitudinal axis of the blade is continuous, or substantially continuous, with the longitudinal axis (i.e., the reciprocating axis) of the drive shaft. The blade receiving portion may be arranged and constructed to as to be capable of receiving blades having a variety of different thickness. Further, a slot preferably extends from the blade receiving portion along the longitudinal axis of the rod. The slot is preferably designed to guide the blade into the blade receiving portion and to support the blade during operation.
In another embodiment of the present teachings, the rod may include an aperture that extends in a lateral direction of the rod (i.e., a direction perpendicular to the longitudinal or reciprocating axis of the rod). Further, the aperture preferably communicates with the rod slot and the aperture is preferably defined substantially perpendicular to the rod slot. A pushpin may be slidably disposed within the aperture. For example, the distal end of the pushpin may be selectively moved so as to contact or abut a side face of the blade when the blade has been inserted into the rod slot and blade receiving portion of the rod. Therefore, the pushpin can fix the position of the blade within the blade slot, so that the blade does not move or wobble during a sawing operation.
In another embodiment, the sleeve is preferably rotatably mounted around the rod such that the sleeve can rotate or pivot about the longitudinal axis of the rod (or drive shaft). The distal end of the sleeve preferably includes an opening (e.g., a slot) designed to receive the blade. For example, the sleeve opening is preferably designed so that the blade projections may pass through the sleeve opening and into the blade receiving portion of the rod. Further, the sleeve preferably rotates or pivots about the longitudinal axis between a blade locking position (e.g., a blade clamping position) and the blade replacement position. As noted above, the collar and sleeve are preferably arranged and constructed such that rotation or pivoting of the collar will cause the sleeve to rotate or pivot. That is, the collar selectively engages the sleeve in order to rotate or pivot the sleeve to the blade replacement position.
In another embodiment, a cam surface is preferably defined on an inner surface of the sleeve. Further, the cam surface is preferably designed to slidably contact or abut a head portion of the pushpin. In addition, the cam surface is preferably designed such that rotation of the sleeve in a first direction causes the pushpin to extend further into the rod aperture and the blade slot. Thus, rotation of the cam surface in the first direction urges the pushpin towards the blade, so as to lock or clamp the blade within the blade slot of the rod.
On the other hand, rotation of the sleeve in a second (opposite) direction preferably permits the pushpin to withdraw from the blade slot defined in the rod so as to permit a blade to be withdrawn from or inserted into the blade slot. As a result, when the sleeve (and thus the cam surface) rotate in the second direction about the longitudinal axis of the rod, the pushpin may be withdrawn from the blade slot and release contact with the side face of the blade that is inserted in the blade slot.
In another embodiment of the present teachings, a first stopper is preferably disposed on the sleeve in order to accurately define the blade replacement position of the blade clamp. For example, the first stopper preferably restricts the sleeve from further rotating or pivoting in relation to the rod when the blade replacement position has been reached. In one representative embodiment, the first stopper may be defined on the cam surface of the sleeve. In another representative embodiment, the first stopper may be defined on an outer surface of the rod.
In another embodiment, the collar preferably includes a tab or other gripping member that enables the operator to manually rotate or pivot the collar with respect to the housing. Therefore, the operator can manually rotate or pivot the tab when the operator wishes to remove and/or change the blade. Preferably, when the sleeve is disposed in the initial position and/or the blade locking or clamping position, the blade receiving portion and blade slot of the rod do not align with the sleeve opening (slot). Therefore, the blade projections can not pass through the sleeve opening and the blade can not be removed from the blade clamp. Moreover, if a blade is not inserted into the blade clamp when the blade clamp is disposed in the initial position, a blade can not be inserted into the blade slot and the blade receiving portion, because the sleeve opening is not aligned with the blade slot and the blade receiving portion.
On the other hand, when the sleeve is disposed in the blade replacement position, the blade slot and the blade receiving portion of the rod preferably align with the sleeve opening (slot). Therefore, the blade projections can easily pass through the sleeve opening of the sleeve and the blade can be inserted into or removed from the blade slot of the blade clamp.
If a first stopper is utilized to restrict the sleeve from pivoting or rotating past the blade replacement position, the sleeve can be accurately positioned in the blade replacement position by simply adjusting the positional relationship between the sleeve and the rod. In this case, the collar tab or gripper member is only required to pivot or rotate the sleeve. The positional relationship of the collar tab with respect to the sleeve (or an aperture in the tool housing) is not significant. Therefore, the sleeve can be accurately and reliably positioned in the blade replacement position without requiring the positional relationship of the housing, the collar, the rod, the sleeve, etc. to be accurately defined.
When the blade clamp is returned to the blade locking position after blade replacement, the distal portion of the sleeve prevents the blade projections from passing through the sleeve opening. Therefore, the blade is reliably retained within the blade clamp. As noted above, when the sleeve is rotated or pivoted toward the initial position, the cam surface of the sleeve pushes or urges the pushpin toward the side face of the blade. Consequently, the blade is reliably and firmly retained between the pushpin and a wall surface of the blade slot, which wall surface is defined within the rod. The sleeve fixes the blade in the clamped or locked state when the sleeve pivots or rotates from the blade replacement position towards the initial position.
As noted above, the sleeve is preferably biased or urged toward the initial position. For example, a torsion spring may be disposed around the rod and may be coupled to the sleeve so as to bias the sleeve toward the initial position. The torsion spring may therefore impart a force to the pushpin, which force will reliably retain the blade between the pushpin and the side wall of the blade slot. By using a torsion spring disposed around the rod, the length of the blade clamp along the axial direction of the drive shaft can be minimized.
The sleeve optionally also may include a second stopper. The second stopper also may restrict the pivotal range of the sleeve with respect to the rod. For example, the second stopper may be disposed in a position, so that the sleeve will be prevented from pivoting past the initial position. That is, the second stopper may define the initial position. If the second stopper restricts the pivotal range of the pushpin (and thus the sleeve), the collar and the sleeve can be designed such that the collar will not contact the sleeve in the initial position as well as the blade locking position. Therefore, if the jigsaw is accidentally started without attaching a blade to the blade clamp, the collar and the sleeve will not be damaged.
Thus, the first stopper may be defined at one end of the cam surface (or the outer surface of the rod), so that the first stopper will contact or abut the pushpin when the sleeve reaches the blade replacement position. Further, the second stopper may be defined at the other end of the cam surface (or the outer surface of the rod), so that the second stopper will contact or abut the pushpin when the sleeve reaches the initial position.
In another embodiment of the present teachings, the cam surface of the sleeve is preferably designed so as to not actively push or urge the pushpin when the sleeve rotates or pivots from the blade replacement position to a push start position. The push start position may be defined at a predetermined angle displaced from the blade replacement position. Thereafter, the cam surface will push or urge the pushpin when the sleeve is rotated or pivoted past the push start position towards the initial position.
The rotation angle of the cam surface may include a range of play. In this range, the cam does not push or urge the pushpin toward the side surface of the blade when the sleeve rotates or pivots between the blade replacement position and the push start position. Thus, as the sleeve rotates or pivots from the blade replacement position to the push start position, the pushpin is preferably not urged or biased to contact the side surface of the blade, which has been inserted into the blade slot and the blade receiving portion. Therefore, rotation of the sleeve is not restricted between the blade replacement position and the push start position. As a result, the sleeve can be reliably rotated or pivoted as far as the push start position regardless of the thickness of the blade and the sleeve will support the blade projections to prevent the blade from falling out of the blade clamp.
If the blade is thick and the cam surface does not include a range of play within rotational angle, the pushpin may contact the blade before the sleeve has sufficiently rotated toward the blade locking position. Consequently, further rotation of the sleeve may be restricted or prevented and the blade may not be securely retained within the blade clamp. The provision of a range of play ensures that the sleeve can sufficiently rotate so as to prevent the blade from dropping out of the sleeve opening.
When the sleeve is further rotated or pivoted beyond the push start position toward the initial position (i.e., toward the blade locking position), a friction angle may defined between (1) a common normal at a contact point of the cam surface and the pushpin and (2) a line passing through the contact point and the rotational center of the cam surface. The friction angle from the push start position to the initial position is preferably within the range of 12-16xc2x0.In other words, the fiction angle is defined between a common tangent at the contact point and a straight line perpendicular to a line passing through the contact point and the center of rotation of the cam. As the friction angle increases, the force exerted against the pushpin (i.e., the blade clamping force) decreases, thereby reducing the possibility that the pushpin will catch the cam surface. A friction angle within the range of 12-16xc2x0 provides (1) sufficient clamping force for the blade within the angle range in which the sleeve pivots from the push start position and (2) also prevents the pushpin from catching on the cam surface.
In another aspect of the present teachings, a rounded portion of the sleeve opening (aperture) preferably includes a tapered face that is preferably defined to guide the blade into the blade slot. Thus, when the sleeve rotates from the blade replacement position to the push start position, the base end of the blade will be guided along the tapered face. Accordingly, the base end of the blade will be correctly positioned within the blade receiving portion and the sleeve can smoothly rotate.
In another aspect of the present teachings, a gap between the sleeve and the rod may be sealed with a sealing member. The sealing member may preferably include a lock portion. The rod may include a groove for receiving the lock portion. When the lock portion is fitted into the groove, the sealing member is prevented from separating from the gap between the rod and the sleeve.
In another aspect of the present teachings, the cam surface of the sleeve is preferably treated or coated in order to prevent the cam surface from seizing to the pushpin, thereby ensuring that the sleeve can smoothly rotate or pivot. For example, the cam surface may be coated with electroless nickel plating.
These aspects and features may be utilized singularly or in combination in order to make improved blade clamping or blade fastening devices, including but not limited to blade clamps suitable for use with jigsaws. In addition, other objects, features and advantages of the present teachings will be readily understood after reading the following detailed description together with the accompanying drawings and the claims. Of course, the additional features and aspects disclosed herein also may be utilized singularly or in combination with the above-described aspects and features.